The present invention relates to an apparatus of and a method for mirror-polishing chamfered outer circumferential edges of a substantially circular plate-shaped work such as a semiconductor wafer, a magnetic disc substrate made of an aluminium or a ceramic, and an optical disc substrate made of a glass.
FIG. 8 is a view showing a circular plate-shaped work 1 having chamfered outer circumferential edges 2a and 2b formed on both the front and back sides of the work. Apparatuses for polishing the outer circumferential edges 2a and 2b of such a work 1 have been well known, such as those disclosed in Japanese Unexamined Patent Application Publication Nos. 2-301135 and 3-26459. In fact, the known polishing apparatuses are all formed in a manner such that their polishing actions can be produced only by pressing a drum-like or a disc-like polishing member (adhesively covered by a polishing cloth) against the outer circumferential edges of a work. As a result, since the contact between the polishing member and the work is substantially concentrated at only one point, the polishing process has only a low efficiency, thus resulting in a low productivity.
In order to solve the above problems, Japanese Unexamined Patent Application Publication No. 7-40214 has suggested that an improved polishing member (buff) having an arcked working surface be used to polish the outer circumferential edges of a work. With the use of an improved polishing apparatus having such an improved polishing member, since it is allowed to carry out a desired polishing process by virtue of a linear contact between the arcked working surface and the outer circumferential edges of a work, it becomes possible to improve the polishing efficiency, thereby allowing the polishing process to be completed in a shortened time period.
However, the above-described improved polishing apparatus has been found to have the following problems. Namely, the disclosed polishing apparatus is formed in a manner such that the working surface of its polishing member has a recess groove engageable with the outer circumferential portion of a work. By engaging the outer circumferential portion of the work into the recess groove formed on the working surface of the polishing member, the outer circumferential edges 2a and 2b on both surfaces of the work as well as an outer periphery surface 3 located between the two outer circumferential edges are pressed against the two side walls and the bottom wall of the recess groove, thereby carrying out an instant polishing treatment. In fact, the above construction and the polishing manner have been found to be responsible for the following problems.
(a) Since the outer circumferential edges of the work have all been formed into inclined surfaces, forces produced by the edges and pressing incliningly against the two side walls of the recess groove will be larger than a force produced by the outer periphery surface of the work and pressing perpendicularly against the bottom wall of the recess groove. As a result, the polishing efficiency is low. In particular, if the polishing member has worn away, it will be more difficult to apply a desired polishing load to the edges.
(b) Since the depth and the shape of the recess groove have to be altered in accordance with an outer circumferential shape of the work as well as its edge chamferring angle q, a cutting process for shaping the recess groove will be extremely difficult, rendering it necessary to prepare various different types of polishing members having different depths and different shapes, thus making the production management difficult.
(c) Since during the polishing process the work and the recess groove have to be made mutually coincident in their positions, it is difficult to control the operations of both the work and the recess groove.
It is an object of the present invention to solve the aforementioned problems present in the above-described conventional polishing apparatus, by using an improved polishing member having an arcked working surface, thereby making it possible to effectively and exactly polish the outer circumferential edges of a work, allowing the polishing treatment to be completed in a shortened time.
In order to achieve the above object, a polishing apparatus for polishing outer circumferential portions of a circular plate-shaped work is formed by including a chuck means which is provided for chucking the circular plate-shaped work having chamfered outer circumferential edges formed on the front and back sides thereof and which is also capable of turning the circular plate-shaped work about the axis thereof, the apparatus also including a pair of edge polishing members having arcked working surfaces for polishing the edges, at least one outer periphery surface polishing member having an arcked working surface for polishing the outer periphery surface of the work. Specifically, the pair of edge polishing members are arranged in a manner such that the respective axes thereof are inclined with respect to the axis of the work held on the chuck means, so that the working surface of one polishing member is in contact with the edge on the front side of the work, while the working surface of the other polishing member is in contact with the edge on the back side of the work. In particular, the outer periphery surface polishing member is located in a position different from the edge polishing members, in a manner such that the axis of the outer periphery surface polishing member is parallel to the axis of the work.
With the use of the polishing apparatus of the present invention having the above-described constitution, since the arcked working surfaces of the polishing members can form a linear contact with the outer circumferential portions of the work, and since the pair of polishing members can be exactly and uniformly pressed against the edge portions on both sides of the work, polishing efficiency can be improved, thereby making it possible to complete the polishing treatment in a shortened time. Further, since it is not necessary for the working surface of each polishing member to form a recess groove, the constitution of each polishing member is relatively simple, ensuring that positions effecting contact between the work and polishing members can be easily changed.
According to a detailed embodiment of the present invention, the working surface of each edge polishing member is formed into a recess curved surface capable of forming a linear contact with an edge of the work in an inclined state, while the working surface of the outer periphery surface polishing member is formed into another recess curved surface capable of forming another linear contact with the outer periphery surface of the work, each of the working surfaces is not formed with a recess groove for engaging with an edge portion of the work, thereby making it possible to freely change polishing positions.
According to one embodiment of the present invention, the polishing apparatus has a pair of edge polishing members and a pair of outer periphery surface polishing members, the two pairs of the polishing members are located in different positions with one polishing member being 90 degrees different from another polishing member when arranged around the chuck means, and with two members of each pair facing each other.
According to another embodiment of the present invention, the polishing apparatus has a pair of edge polishing members and one outer periphery surface polishing member, these polishing members are located in different positions with one polishing member being 120 degrees different from another polishing member when arranged around the chuck means.
According to one detailed embodiment of the present invention, the polishing apparatus includes moving mechanisms for moving the edge polishing members in a direction parallel to the axis of the apparatus, linear guide mechanisms for freely movably supporting the edge polishing members so that they are freely movable in a direction perpendicular to the axis of the apparatus, load adding means for urging the respective edge polishing members against the outer circumferential edges of the work, the polishing apparatus includes another moving mechanisms for moving the outer periphery surface polishing members in a direction parallel to the axis of the apparatus, another linear guide mechanisms for freely movably supporting the outer periphery surface polishing members so that they are freely movable in a direction perpendicular to the axis of the apparatus, another load adding means for adding polishing load by urging the respective outer periphery surface polishing members against the outer periphery surface of the work.
Specifically, each of the moving mechanisms for moving the edge polishing members includes a ball screw freely rotatably supported on the apparatus main body and rotatably driven by a motor, a nut member movable back and forth by virtue of the rotation of the ball screw, and a movable table connected with the nut member and integrally movable with the nut member, while each of the linear guide mechanisms is provided to freely movably support a polishing member on a movable table, and each load adding means is formed by an air cylinder or a weight which can pressingly urge a holder.
In particular, each moving mechanism for moving an outer periphery surface polishing member includes a ball screw freely rotatably supported on a movable table and rotatably driven by a motor, a nut member movable back and forth by virtue of the rotation of the ball screw, and a support member connected to and integrally movable with the nut member, the support member supporting one outer periphery surface polishing member, while each linear guide mechanism for guiding an outer periphery surface polishing member is provided to freely movably support a movable table on the apparatus main body, and each load adding means is formed by an air cylinder or a weight which can pressingly urge a holder.
According to another detailed embodiment of the present invention, the polishing apparatus includes moving mechanisms for relatively moving the edge polishing members and the chuck means in a direction of the axis of the work, linear guide mechanisms for freely movably supporting the edge polishing members so that they are freely movable in a direction perpendicular to the axis of the apparatus, load adding means for urging the respective edge polishing members against the outer circumferential edges of the work, the polishing apparatus further includes another moving mechanisms for moving the outer periphery surface polishing members in a direction parallel to the axis of the apparatus, another linear guide mechanisms for freely movably supporting the outer periphery surface polishing members so that they are freely movable in a direction perpendicular to the axis of the apparatus, another load adding means for adding polishing loads by urging the respective outer periphery surface polishing members against the outer periphery surface of the work.
Furthermore, according to the present invention, there is provided a polishing method for polishing outer circumferential portions of a circular plate-shaped work, characterized in that a circular plate-shaped work having chamfered outer circumferential edges is turned about the axis of the work, while at the same time a polishing treatment is performed using a pair of edge polishing members each having an arcked working surface and also using at least one outer periphery surface polishing member, with the axes of the pair of edge polishing members being inclined with respect to the axis of the work held by the chuck means, in a manner such that the working surface of one edge polishing member gets in contact with an edge portion on the front side of the work, while the working surface of the other edge polishing member gets in contact with an edge portion on the back side of the work, and with the axis of the outer periphery surface polishing member being parallel with the axis of the work so as to enable the working surface of the polishing member to get in contact with the outer periphery surface of the work, while at the same time using load adding means to press the edge polishing members and the outer periphery surface polishing member against the work so as to add a desired polishing load, thereby simultaneously polishing the outer circumferential edges and the outer periphery surface of the work by virtue of these polishing members.